Angle hand piece



Dec. 6 1938. c. L. STOLTE ET'AL I 291389945 ANGLE HAND PIECE Filed March 19, 1937 INVENTOR.

CHAPLEE L.$TOLT 1 Patented Dec. 6, 1938 UNITED STATES PATENT OFFICE Application March 19,

1 Claim.

Our invention relates to an improvement in dental tools of the type known as angle hand pieces, which are transmission appliances for the application of power to drills and such like tools used by dentists working upon teeth in the practice of their profession.

Hand pieces, angle and otherwise, are old in the art anda great many forms of them have been in use for many years and we do not claim angle hand pieces broadly, but only the improvement therein hereinafter set forth and described in detail.

One object of our invention is a hand piece that is as compact as usual but has an adjustment whereby Wear may be taken up in a much better manner and to a greater degree than heretofore possible.

Another object of our invention is a construction that will normally wear several times as long as hand pieces commonly manufactured. The principal and most beneficial object of this, our present, invention is a hand piece that will not chatter the tool since chattering of the tool when it is being used not only greatly increases the discomfort of. the person whose teeth are being operated upon, but it prevents the dentist from doing his best work,

These and other objects apparent from this specification and claim constitute the purposes of our present invention.

We accomplish the objects enumerated by the structure illustrated in the accompanying drawing, which for the sake of clarity is many times larger than the actual structure, it being understood that the completed hand piece is of such size that it may be readily used for the purpose intended.

In the drawing- Fig. I is a side view partly in section of our new hand piece;

Fig. II is a top or plan view of Fig. I; and

Fig. III is a bottom View of Fig. I.

A housing 5, is interiorly formed to contain a working spindle 6, which in turn is adapted to receive the tool 1, and a retainer 8, pivotally attached to the housing 5, by the screw 9, works in a slot 50., that is provided as shown in the housing 5, and engages the tool I, in the way well known to the art.

Mounted upon the spindle 6, and rigid therewith is a spur gear in, which meshes with the spur gear I I, made rigid with the jack-drum l2.

At the other end of the jack-drum I2 is the mitre gear l3, which is made rigid with the jackdrum l2. The mitre gear I3 is arranged to mesh 1937, Serial No. 131,887

with a companion mitre gear It, provided with a drum bearing Ma, and receives rotative powerthrough the shaft !5 in the well known manner from a power source not shown. The jack-drum I2 is .rotatably mounted on the relatively fixed spindle 26 which I have shown to be screw threaded into a hole formed in the housing 5.

Upon the lower end of the spindle 6 is a tapered journal 60., which runs Within the adjust able tapered lower bearing It. The taper of this lower bearing I6 and its contained tapered journal 6a, is an important matter and it has been found that the ideal angle, indicated by A in Fig. I, is 8%; degrees. It cannot be made sub stantially less than 7 degrees without danger of seizure and should not be greater than 10 degrees to get good results.

Both the tapered journal 6a and the lower bearing I6 should be hardened and highly polished.

The upper or opposite end of the spindle 6 is likewise provided with a tapered journal 62), and within the housing 5, preferably pressed rigidly in place, is a hardened and polished tapered bearing l'l, adapted to act as a bearing for the journal 61).

The taper of 6b and I1 is considerably greater than that of the lower bearings 6a and i6 since the load on it is almost entirely a thrust load, when any loadis applied to it. It has been found that 14 to 16 degrees of angle is preferable for these two elements which will of course agree, the median angle of 15 degrees being deemed the best.

All of the interior working parts of this hand piece, including the mitre gears l3 and [4, the jack-drum l2 and all gears mounted thereon and also the fixed spindle 26, should be of steel, hardened and highly polished.

A laminated shim member 20, the laminationsof which are approximately .002 in thickness, provides means for adjusting the main spindle by increments of about .0003" An oil hole 2| provides means for introducing lubrication to the interior of the hand piece, which if properly made will be substantially oil tight.

By mounting the mitre gears as shown with the spur gear beneath, several important results are attained. First, the thrust of the drive is against the bearing I6 which if made within the limits of the angles indicated will run even better than a straight journal, while providing adjusting means.

By using spur gears, which is now possible, the

adjustment merely displaces the faces of the gear teeth of the gears II and I without disturbing their mesh or the relative position of their respective pitch circles, something that is obviously impossible with the mitre gear drive heretofore used.

Dental motors are now uniformly of 3600 R. P. M. nominal speed, usually preferable to any slower speed for revoluble dental tools. Rheostats are provided for slowing the speed of the motor where conditions demand it and have heretofore been found necessary with angle hand pieces in all cases because of wear in the tool holding spindle putting the very critical mitre gears out of proper mesh. With my new construction the high speed can be used when wanted because the mitre gears are so placed that they are not affected by spindle wear and the spur gears, that are so affected, move axially leaving the gear pitch circles undisturbed with the result of a far smoother running tool and one that lasts several hundred hours without major overhaul.

It will also be noted that when in use the spindle 6 will ride closely within the adjustable lower bearing l6, which will prevent the exudation of any oil that may be used to lubricate the hand piece, the tendency being to keep it sealed. This construction eliminates a difiiculty long tolerated since the remedy was not apparent.

Owing to the direction of rotation, the threads 16a on the adjustable bearing l6 will ordinarily be made left handed and should be very fine, say about threads to the inch or finer.

It will be found that in use the journal 6b and the upper bearing l1, sustain an extremely small amount of wear due to use since the lower bearing 16 and the journal 6a carry substantially the entire gear thrust load.

It will also be found that the construction of the lower bearing to the taper indicated and described, results in a smooth running tool, almost entirely noiseless, which permits the dentist using the same to execute far better work than with a tool as commonly constructed, and which will, at the same time, relieve his patient of a great part of the annoyance commonly incident to the operation of such a tool since the only vibration he experiences is that of the tool itself when cutting the tooth substance.

The explanation for this remarkable condition is thought to be that the thrust load is always carried by one bearing independent of the other. Downward hand pressure by the dentist is carried by the upper hearing I! while side thrust, as in cutting, will generally be in a direction opposite to the thrust of the gears l0 and II, with the lower bearing carrying the load substantially independent of the upper one.

But whatever the reasons may be, if the angle hand piece is constructed as directed and described, the result will be surprising to any dentist that has heretofore used only hand pieces constructed after the usual manner. With our new hand piece a beneficial result is produced in that it is smoother in operation, does not chatter the tool and permits the dentist to feel his work rather than the vibration of the tool.

Bearing in mind that the drawing is disproportionate as to size, for the purpose of more clearly illustrating the construction, it may be followed very closely in actual constructive practice.

End bearing surfaces for the jack drum l2 may be formed by a boring tool through the hole provided for the fixed spindle 26. After finishing, the first step will be to press the hearing I! in place. Then the jack drum may be inserted through the opening provided for the bearing 16 and back far enough out of the way so that th spindle 6 can be inserted.

The fixed spindle 26 is next put in place and afterwards the assembly represented by the mitre gear M the bearing [50. and the shaft [5 is screwed into place when the assembly is complete.

The housing should be of one piece construction and can be of an easily machinable close grained metal that will plate to advantage.

Having disclosed our invention so that anyone skilled in the art to which it appertains can make and use it what we claim as new and desire to secure by Letters Patent, is:

In an angle hand piece, a housing member, a tool carrying spindle rotatable mounted within said housing, an angle gear drive for said spindle, an adjustable tapered lower bearing for said spindle tapered approximately 8 degrees as specified and a fixed tapered upper bearing for said spindle having a taper exceeding the taper of the said lower bearing.

CHARLES L. s'ro T PAUL BRONG. 

